Work in progress and for the coming year will concentrate on the detection of L-form fragments in human cells in tissue culture once infected with this organism but now undetectable by viable count. The direct fluorescent antibody technique will be used for these studies. Also, this physiological L-form before and after growth in tissue culture will be examined and compared for a quantitative estimation of the amount of hemolysis and M protein being produced. Finally, this L-form will also be investigated for changes in its antibiotic sensitivity patterns before and after being passed in human heart cell tissue cultures.